A unique aspect of this proposal is that it outlines a series of experiments to be performed on an animal model, the rhesus monkey, which is taxonomically and phylogenetically closer to humans than other animal models commonly used to study temperature regulation and adaptation. Recent studies have demonstrated that the basic mechanisms utilized for effective acute temperature regulation as well as long term heat and cold adaptation in this primate are similar to that of man. These similarities are highly significant since the studies described in this proposal will subject the rhesus monkey to experimental procedures which are impossible in humans. Skin biopsies taken before and during long term heat acclimatization will be used to quantitate the enzymatic and biochemical changes in the eccrine sweat gland associated with the process of heat acclimatization in higher primates. Intravenous and intrahypothalamic infusion techniques will be used to assess the physiological role of plasma and brain tissue sodium and calcium ratios in the control of body temperature in non-exercising higher primates. These procedures will also be used to quantitate the interrelationships between gonadal hormones and temperature regulatory responses of hyperthermic primates and assess the role of active vasodilator mechanisms in higher primates. The experiments outlined in this proposal will provide new important information about the control of the basic effector mechanisms involved in temperature regulation and adaptation in primates, including man, which may be important in providing better and more physiological treatment of hyperthermic patients.